A central element in the use of regenerative energy sources in an electricity grid but also in the energy supply for mobile consumers, for example, motor vehicles with an electric drive, is buffer storage means. They serve to be able to compensate for the volatility in terms of the supply feed of electric power by the sources and consumption by sinks for the electric power. Without a buffer storage means at any moment in time only the amount of electric power that is just being generated at the given time can be transported and/or provided for the consumers or sinks. By virtue of the volatility both of the sources and also the sinks it is thus not possible to ensure supply reliability.
The buffer storage means must be able to compensate in particular for short-notice and short-term fluctuations on the part of the sources and sinks. An example of this is the “kick-down,” that is to say, the short-notice implementation of the acceleration control device of an electrically driven motor vehicle. However, grid fluctuations by virtue of short-term weather changes in a supply grid involving a large proportion of renewable energy sources and short-notice load fluctuations constitute a suitable example in terms of the necessity for compensating mechanisms. The buffer storage means must therefore be able to both deliver and also receive power in a dynamic and variable fashion.
In that respect a distinction can be drawn between various kinds of demand situations for the buffer storage means:
1. bridging longer-term periods as far as seasonal storage means,
2. balance-sheet storage for compensating for deficits and surpluses in an electricity grid,
3. compensating for short-notice and time-limited deficits and surpluses as occur for example by virtue of grid fluctuations in an electricity grid in order to stabilize the grid,
4. buffer storage means for a digital end point in a routed supply grid involving packet-based transmission as well as gateways or interfaces of such a routed supply grid involving packet-based transmission to the classic ohmic electricity grid,
5. a demand arising out of new concepts for electricity grids like for example packet-based current transport, and
6. demand scenarios as occur, for example, in the power supply of electrically driven modes of transport like automobiles, ships and aircraft.
In that respect, in principle, two situations which are to be distinguished from each other occur, namely, on the one hand, that the electric power required by a sink or a plurality of sinks at a moment in time exceeds the power afforded by the sources at that time, and on the other hand, that the power provided by the sources at a moment in time is greater than the power required by the sinks at the same time.